1. Field of the Invention
The present invention relates to an automotive air conditioning system having a hot water type heater core for heating air using hot water as a heat source and a coolant-refrigerant heat exchanger for heating hot water using a refrigerant discharged from a compressor in a refrigeration cycle as a heat source, and more specifically to an automotive air conditioning system which is effective when applied to vehicles having a fuel cell installed therein, electric vehicles or hybrid vehicles in which less waste heat is generated from the engine installed therein.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 11-208250 discloses a hot water circuit configuration for a conventional automotive air conditioning system having a hot water type heater core for heating air using hot water (coolant) from an engine installed in a vehicle as a heat source, which hot water circuit configuration increases the heating performance inside a passenger compartment before the engine has warmed up.
In this related art, a bypass pipe is provided to connect a hot water inlet pipe to a hot water outlet pipe of the hot water type heater core, and opening and closing valves are provided at locations along the hot water inlet pipe and the hot water outlet pipe, respectively, which are closer to the engine side than the connecting portion of the bypass pipe.
Therefore, by closing the opening and closing valves, a local closed circuit is formed at a location in the vicinity of the hot water type heater core by the hot water type heater core and the bypass pipe. A hot water heater using an electric heater and an electric pump are provided in the local closed circuit.
By adopting this construction, before the engine of the vehicle has warmed up, both the opening and closing valves are closed, the electric pump is activated and the electric heater is energized, so that water inside the local closed circuit is heated by means of the electric heater. As this occurs, since the electric heater only has to heat a small amount of water within the local closed circuit, the speed at which the temperature of the water is increased increases, so that the heating performance in the passenger compartment is increased before completion of warming up of the engine of the vehicle.
In the related art, while the amount of water that is to be heated by the electric heater is limited, since the specific heat of water is very high, it takes time to heat water to a predetermined temperature by means of the electric heater, and the immediate effectiveness in heating the interior of the passenger compartment is insufficient.